UPD17717 Datasheet, PDF (41/408 Pages) NEC – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DEDICATED HARDWARE FOR DIGITAL TUNING SYSTEM

µPD17717, 17718, 17719
4.4 Cautions on Using Data Memory
4.4.1 At power-ON reset
The contents of the general-purpose data memory are “undefined” at power-ON reset.
Initialize the data memory as necessary.
4.4.2 Cautions on data memory not provided
If a data memory manipulation instruction that reads the data memory is executed to a data memory address
not provided, undefined data is read.
Nothing is changed even if data is written to such an address.
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